On R-triviality of F4, II

Simple algebraic groups of type F4 defined over a field k are the full automorphism groups of Albert algebras over k. Let A be an Albert algebra over a field k of arbitrary characteristic whose isotopes are all isomorphic. We prove that Aut(A) is R-trivial, in the sense of Manin. If k contains cube roots of unity and A is any Albert algebra over k, we prove that there is an isotope A(v) of A such that Aut(A(v)) is R-trivial